Added max line length = 80 for jshint

[syranide]

Ever so slightly more like your internal FB-linting.

[zpao]

I might revert this, but haven't decided. The 80 chars is a strong suggestion, but I mostly trust humans to break the rules where it makes sense. That URL should remain on a single line so it's copy-pastable.

That said, we've come back multiple times with "make this fit in 80" so perhaps it makes sense to have but make it a warning but not fail lint (I'm not sure that's even possible)

[syranide]

@zpao Feel free! I suggested it only becuse make this fit in 80 and it's hard to check otherwise The problem with keeping lines longer than that in the rep is that jshint will complain for all files, all the time, and it didn't seem to be easily fixable. So if there ends up being a lot of URLs, the lint will become useless again.